1. Field of the Invention
The present invention relates to control systems for controlling movement of loads in a test environment.
2. Description of the Prior Art
U.S. Pat. No. 3,913,389, issued Oct. 21, 1975 to Larson, illustrates a circuit for compensating overturning moments on a test table and specimen arrangement that is being controlled in horizontal and vertical planes by hydraulic actuators. The control system includes means to provide a compensation signal to the servovalve control loop for compensating for the overturning moment on the specimen. The center of gravity of the specimen is offset from the central plane of the horizontal actuator moving the table and specimen.
The present invention is related to the F.sub.H signal illustrated in FIGS. 2 and 3 of the drawings of U.S. Pat. No. 3,913,389. Similar to that patent a compensating signal for performance degrading specimen disturbances is injected into the basic servo hydraulic position control loop. The present invention's technique for obtaining the compensating signal is much more accurate and can be used to compensate for more general loads. This enables more precise control without readjustment of the electronic system with changing general specimen loads.
Compensating the servovalve control circuit for linearization as shown and described in U.S. Pat. No. 4,336,745 is desired for providing a servovalve output which is linear with respect to its input signal. When such linearization is provided the additional compensation signal of the present invention provides optimum compensation.